The present invention relates to a terminal equipment switching control technique, and more particularly to a terminal switching apparatus and method based on a terminal equipment switching control technique which is suitable for improving the operability and reliability at the time of generation of a terminal equipment failure by multiplexing terminal equipments.
The recent popularization of personal computers has exhibited the rapid increasing use of an ordinary general-purpose terminal equipment such as a personal computer as a terminal equipment coupled with a central processing unit or a server in an on-line manner. Merits of the use of a personal computer lie in that the cost of the personal computer itself is low and that network application software worldwidely popularized can be utilized as it is. However, though the cost of the personal computer is low, the shortening of the developing period or cycle of the personal computer results in that the reliability of the personal computer is low, in many cases, as compared with the conventional dedicated equipment for the exclusive use as a terminal.
Hitherto, a failure rate has been lowered by improving the reliability of a terminal equipment itself for exclusive use as an on-line terminal to reduce the influence of a failure of the terminal equipment on a service or work. However, a terminal equipment using a generally popularized low-cost personal computer has a high failure rate and is therefore considered as being unsuitable for an on-line processing in which an important service is performed.
Techniques relevant to the present invention include a technique disclosed by JP-A-6-224914. In the disclosed technique, a backup or monitor terminal and a terminal operation checking file for storing the operating conditions of service operating terminals are provided on the same network. The monitor terminal periodically monitors the terminal operation checking file to detect the abnormality of each service operating terminal. The monitor terminal takes over the service of an abnormal terminal. With this construction, it becomes possible to reduce the influence of a terminal failure on an on-line service, that is, it becomes possible to make a low-reliability terminal adaptable as an on-line terminal.
According to such a technique, each terminal equipment has a need for incorporation of a dedicated processing for storing the normality of that terminal equipment into the file on an on-line network. When the operation/maintenance is taken into consideration, the above requisition makes the cost high in the case where the number of terminal equipments is large. Further, since the monitoring of the condition of communication and on-line transmit/receive data between the terminal and a host computer and the monitoring of data being inputted by an operator into a display screen are not possible, there is a possibility that when a console exchange occurs, the on-line data has an omission or the data being inputted by the operator is erased. For example, in the case where a certain terminal equipment is switched to a spare terminal as the result of generation of a failure in that terminal equipment when the host computer is transferring an important message to that terminal equipment, there is a possibility that the message is not normally transferred to the spare terminal. In such a case, it is not possible to inform an operator of the message even if the switching to the spare terminal is made.
An object of the present invention is to provide a technique with which at the time of generation of a failure in any one of plural terminal equipments connected to a host computer in an on-line manner, the switching to a spare terminal equipment is performed smoothly with no influence on a service while ensuring on-line data handled between the host computer and the faulty terminal equipment or data operated by an operator, whereby low-cost terminal equipments are made adaptable as terminal equipments for on-line service even if the reliability of each terminal equipment is low.
In a terminal switching system according to the present invention, a terminal switching apparatus is provided on an on-line network between an information processing apparatus as a system body and terminal equipments which are under the control of the terminal switching apparatus and are made as the objects of switching. The terminal switching apparatus includes a screen data storage memory for each terminal equipment in which screen data, input data, cursor position and mouse position are stored, an on-line data storage memory for each terminal equipment in which on-line transmit/receive data between that terminal equipment and the information processing apparatus is stored, an on-line control section for performing an on-line control, a terminal failure detection section for detecting the abnormality of each terminal equipment, and a switching control section for performing the switching between the terminal equipments. In the case where the terminal failure detection section detects the generation of a failure in any one of the terminal equipments, the switching control section copies the contents of the screen data storage memory and the on-line data storage memory for the terminal equipment with the failure into the screen data storage memory and the on-line data storage memory for a spare terminal equipment and disconnects the faulty operating terminal from operation so that an on-line processing is started with the spare terminal equipment used as an operating terminal equipment, thereby enabling the switching from the faulty operating terminal to the spare terminal equipment while taking over the screen data, on-line data and so forth of the operating terminal equipment immediately before the generation of the failure.
In the case where an operator is performing an on-line processing for the information processing apparatus by use of an operating terminal equipment in an on-line system to which the terminal switching apparatus according to the present invention is applied, screen data, cursor position, input characters, mouse position and so forth handled by the operator are continually preserved in the screen data storage memory. Also, on-line data transmitted from the operating terminal equipment to the information processing apparatus is once stored into the on-line data storage memory of the terminal switching apparatus and is preserved therein until the transmission from the terminal switching apparatus to the information processing apparatus is normally completed. Similarly, on-line data received by the operating terminal equipment from the information processing apparatus is once stored into the on-line data storage memory of the terminal switching apparatus and is preserved therein until the transmission from the terminal switching apparatus to the operating terminal equipment is normally completed.
In the case where any failure is generated in an operating terminal equipment which is being operated by the operator, the terminal failure detection section of the terminal switching apparatus detects the abnormality of that terminal equipment by means of the ceasing of a polling to the terminal equipment, the detection of abnormality in receive data from the terminal equipment, the detection of abnormality in transmit data to the terminal equipment, and so forth. The failure detection section informs the switching control section of the detection of the abnormality. Then, the switching control section displays the contents of the screen data storage memory for the abnormal operating terminal equipment on the spare terminal equipment and transmits the contents of the on-line data storage memory for the abnormal operating terminal equipment to the spare terminal equipment. Thereby, it becomes possible to perform the terminal switching while the contents of input operation by the operator and the contents of on-line transmit/receive data in the faulty operating terminal equipment are taken over to the spare terminal equipment as they are.
With the above construction, the operator is enabled, after the generation of the failure in the terminal equipment under operation, to restart the operation by use of the spare terminal equipment while screen data and on-line data before the generation of the failure are taken over as they are. Also, it is possible to prevent the influence of the terminal failure on an on-line service. According to the present invention, an on-line service using the on-line coupling of terminal equipments to an information processing apparatus as a system body or a server can be operated with no need of the provision of specific high-reliability dedicated terminal equipments and thereinstead by use of the multiple provision of low-cost general-purpose terminal equipments with no hindrance to the service.